Process of producing phthaleins



TED s'rras ALFRED L. RISPLER, OF ST. LOUIS, MISSO URI, ASSIGNOR TO MONSALNTO CHEMICAL- WQRXS, OF 55!. LOUIS, MISSOURI, A. CORPORATION OF MISSOURI.

rename or rnopucme rn rnannnvs.

No Drawing.

To all. whom it map concem:

Be it known that I, ALFRED L. RISPLER, a

citizen of Germany, residing at St. Louis,

Missouri, have invented a certain new and useful Improvement in Processes of Producing Phthaleins, of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the manufacture of hthaleins.

he condensation of 1phthalic anhydrid with phenols involves t e substitution of hydrogen atoms of the aromatic nucleus of the phenols and the removal of oxygen atoms from the phthalic anhydrid with accompanying formation of water. The condensation of'phthalic anhydrid with most phenols will occur only in presence of dehydrating agents, such as concentrated sulfuric acid, anhydrous zinc chlorid or stannic tetrachlorid. As thecondensation reaction progresses, the formation of water likewise progresses, and the water formed dilutes the reaction mixture and the dehydrating agents present and correspondingly retards or inhibits the condensation process. In consequence of the fact that the reaction mixture becomes diluted by the water of reaction, it is not possible to condense perfectl the applied quantity of phthalic anhydri with the phenols.

The use of concentrated sulfuric acid, anhydrous zinc chlorid or stannic tetrachlorid as condensing agents has the disadvantage that tarry by-products are formed which interfere with the refining of the phthaleins and that a subsidiary ortho condensation occurs, the result of whichare anhydrids such phenolphthalein.

as the fluoran in the manufacture of phenolphthalein causing thus a loss of the mate rials applied in the reaction. With above mentioned condensing agents, yields of only $30 to of the theory can be obtalned when used in the condensation oi phthalic anhydrid with phenol for the preparation of One object of my invention is to rovide a process for'producing phthaleins dy which the reaction can be made to procee to substantial completion at a comparatively low temperature.

Another object is to provide a process of the character mentioned by which the desired para substituted phthalein are formed Specification of Letters Patent.

the purpose described t such an acid to bring about the in a high state of purity from which the pure phthaleins are easily obtained.

Another object is to rovide a process for at can be easily controlled so as to bring about a maximum condensation in the para position to the hydroxyl groups.

. And still another object is to provide a process by which phthaleins can be produced without the formation of large amounts of tarry by-products which would interfere w1th the refinin process.

To this end have devised a producing phthaleins, which, riefly' described, consists in using an anhydrous aromatic sulfonic acid or a mixture containing condensatlon of pl tialic anhydrid and phenols. Such a process is superior to the processes heretofore used for producing phthaleins, in that the water formed durin the progress of the condensation reaction is taken up by Patented June 14, 1921 App1i'ca tion filed May 10, 1920. Serial No. 380,412.

rocess for the anhydrousaromatic sulfonic acid in a perfectly into solution a quantity of a suit able anhydrous aromatic sulfonic acid (usually from 200 to 250 lbs.) is added to the mixture and the mixture stirred or agitated until the sulfonic acid has gone into solution. The reaction mass is then kept at a temperature of approximately 120 C. for from ten to twelve hours, after which time the reaction usually is completed. The crude phenolphthalein is then -washed with water to remove the excess of phenol, then dissolved in caustic soda solution, filtered and precipitated with acid, where-after it is recrystallized from alcohol, giving a high grade pure phenolphthalein.

lhe action of the anhydrous aromatic sulfonic acid can be increased when a roportional amount oi anhydrous zinc chlbrid is added to the reaction mass. In the above example, for instance, the 200 to 250 lbs. sulfonic acid may be replaced by a mixture of 175 lbs. sulfonic acid and 50 lbs. anhydrous zinc chlorid. In this case the portion of the sulfonic acid which has 'alread taken up water will act on the zinc chlori under formation of the zinc salt of the sulfonic acid and hydrochloric acid. The latter will distil off from the reaction mass and take along the water of reaction.

In this way the reaction can be carried on to completion and a yield of 195 lbs. phenolis equiva phthalein can be obtained which lent to about 90% of the theoretical yield.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A process for producing phthaleins, characterized by condensing phthalic anhydrid with a phenol in the presence of an anhydrous aromatic sulfonic acid, whereb 100 lbs. of hthalic anhydrid with ap temperature of approximately 120 C. to complete the reaction.

4. A process for. reducing phthaleins, characterized by con ensing p thalic anhydrid with phenols in the presence of an an hydrous aromatic sulfonic acid and zinc chlorid.

5. A process forproducing phenolphthalein, characterized y condensing phthalic anhydrid and phenol in the presence 05- a anhydrous aromatic sulfonic acid.

6. A process for producing phenolphthalein, characterized by heating a mixture of phthalic anhydrid and phenol until the phthalic anhydrid has gone perfectly into solution, adding an anhydrous aromatic sulfonic acid to the mixture and stirring or agitating the mass until the sulfonic acid has gone lnto solution, and maintainin the mass at a temperature of ap roximate y 120 C. until the action is completed...

7. A process for producing phenolphthalein, characterized by mixing approximatel mately 200 bs. of phenol, heating sar mixrox1-.

ture to a temperature of ap roximately P- I (1, adding from 200 to 250 bs. of an anhydrous aromatic sulfonic acid to the mixture and stirring the mass until the sulfonic acid goes into solution, and maintainin the mass at a'-temperature of approximatjy C. for approximatel ten to twelve hours.

' FRED L. RISPLER. 

